<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<style>
    body {
        padding: 50px;
    }
    
    .mydiv {
        height: 200px;
        width: 200px;
        border: 1px solid #ccc;
        margin-bottom: 20px;
        display: inline-block;
        margin-right: 20px;
    }
    /*filter: blur() grayscale() drop-shadow();*/
    /*drop-shadow() 滤镜可接受的参数基本上跟box-shadow 属性是一样
的，但不包括扩张半径，不包括inset 关键字，也不支持逗号分割的多层投
影语法。举个例子，上面的投影：*/
    .case1 {
      background: #000;
      filter: drop-shadow(2px 2px 10px rgba(0,0,0,.5));
    }
    
    .case2 {}
    
    .case3 {}
</style>

<body>
    <div class="mydiv case1"></div>
    <div class="mydiv case2"></div>
    <div class="mydiv case3"></div>
</body>

</html>